1. Field of the Invention
The present invention relates to a method of determining of a physical feature of a medium, comprising: producing radiation with a light source; placing a probe on a sample of the medium, the probe comprising a first optical fiber having a first diameter, and at least a second optical fiber having a second diameter; sending light coming from the light source, through the first optical fiber; collecting first backscattered radiation through the first optical fiber and second backscattered radiation through the second optical fiber; producing a first signal based on the first backscattered radiation, and a second signal based on the second backscattered radiation; and determining a measured differential backscatter signal as a function of wavelength using the first and second signals.
2. Description of the Related Art
Such a method is known, as described in A. Amelink, M. P. L. Bard, J. A. Burgers, and H. J. C. M. Sterenborg, “Single Scattering Spectroscopy for the Endoscopic Analysis of Particle Size in Superficial Layers of Turbid Media”, Applied Optics 42, pp. 4095-4101 (2003); which describes a special device used to determine particle sizes in superficial layers. The device is suitable for measuring particle sizes in, for example, an aqueous suspension with polystyrene spheres, but is not fitted to accurately measure particle sizes in living tissue. So, determining whether living tissue is normal or precancerous, by way of measuring particle sizes in living tissue is not very promising.
As described in R. M. P. Doornbos, R. Lang, M. C. Aalders, F. W. Cross, and H. J. C. M. Sterenborg, “The Determination of In Vivo Human Tissue Optical Properties and Absolute Chromophore Concentrations Using Spatially Resolved Steady-State Diffuse Reflectance Spectroscopy”, Phys. Med. Biol. 44 (1999), pp. 967-981; the optical properties of human tissue are determined in vivo using a spectroscopic arrangement with ten optical fibers. One of the fibers is used to irradiate a sample, and nine other fibers collect the reflected light. By using a multitude of fibers to collect the reflected light, it is possible to calculate scattering and absorption coefficients of the sample. However, the method is not suitable for locally measuring the optical properties of the tissue. In particular, only mean values of the absorption coefficient of a relatively large part of the sample can be determined.